JP3092995B2 - Chitosan composite porous body and method for preparing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite porous material mainly composed of chitosan and vegetable fiber and a method for preparing the same.
The composite porous body can be widely used as an antibacterial porous structure having appropriate mechanical properties in the fields of biotechnology-related materials, pharmaceutical materials, agricultural materials, packaging materials, and the like.

[0002]

2. Description of the Related Art Chitosan is a high molecular substance derived by deacetylating chitin contained in crustaceans such as crabs and shrimps and insects such as beetles. Chitin is produced in the living world in the second largest amount after cellulose, and chitosan derived therefrom, like chitin, is expected to be applied to various fields. For example, separation membrane, food wrapping paper,
Chitosan-based paper used for medical materials, etc.
No. 59499), a film having antibacterial property and antifungal property by attaching chitosan (Japanese Patent Application Laid-Open No. 62-83875).
Etc. In addition, the combination of chitosan and plant fiber is used as a casing material for filling a meat product by treating a paper base with chitosan (Japanese Patent Laid-Open No. 1-174699).
No. 2), an agricultural sheet in which chitosan is applied to a natural pulp sheet (Japanese Patent Laid-Open No. 2-2303), and the like.

On the other hand, there is also an attempt to process chitosan into a porous body and use it. A method of forming a porous body by freeze-drying by combining collagen with chitosan (JP-A-62-238209), and a method of forming a porous body by mixing a chitosan solution with a blowing agent (JP-A-62-16)
7331, JP-A-63-90507) and the like. The porous body thus obtained is expected to be widely applied to medical materials, culture base materials, separation materials, etc. by utilizing its properties. However, in actual use,
Mechanical properties as well as chemical properties become important. Depending on the purpose of use, high breaking strength, high elastic modulus, and the like are required. In such a case, these porous bodies cannot satisfy the necessary conditions,
It is also very difficult to control the mechanical properties.

[0004]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances of the prior art, and has been made in consideration of the above-mentioned prior art, without impairing the properties of chitosan, such as antibacterial properties and biodegradability, and having excellent mechanical properties. The purpose is to provide.

[0005]

This object is achieved by the following means. That is, the present invention is a chitosan composite porous body having a bulk specific gravity of 0.01 to 0.1 g / cc, which is a foamed structure mainly composed of chitosan and plant fiber. The present invention also relates to water, chitosan, vegetable fiber and
The mixed solution obtained by mixing phosphoric acid is foamed, dried and
Structure mainly composed of chitosan and vegetable fiber.
Chitosan complex having a bulk specific gravity of 0.01 to 0.1 g / cc
It is a composite porous body. The present invention also relates to chitosan and plant
A structure mainly composed of fibers, having a bulk specific gravity of 0.01 to
A method for preparing a chitosan composite porous material having a concentration of 0.1 g / cc, wherein a mixed solution obtained by mixing water, chitosan, plant fiber and acid is foamed, dried, and then, if necessary, to a degree of reacetylation of 40. % Or more.

The chitosan composite porous material according to the present invention has a characteristic structure in which chitosan enters a film-like structure in a network structure of plant fibers, and realizes a lightweight and mechanically strong structure. .

[0007] In the present invention, plant fiber (hereinafter, simply referred to as fiber) is wood or cereal fiber derived from wood, cereal or the like. The wood fiber is a fiber derived from conifers such as fir and fir, or a fiber derived from hardwood, and is available as, for example, pulp fiber. The cereal fiber is a fiber derived from the outer skin of soybeans and the like,
For example, soybean pressed residue (okara) and the like can be used. The main component of these fibers is cellulose as long as it is a water-insoluble polymer, has a hydrophilic active group on the surface, and has a property of fixing to chitosan. It is necessary that the fiber has a fibrous shape, and a long fiber is more preferable than a short fiber. This is because long fibers tend to form a stronger skeleton in the chitosan tissue. Therefore, although there is an advantage that it is easy to form a uniform structure simply with finely divided cellulose or the like, when the content of cellulose is small, the reinforcing effect is poor, and in order to impart sufficient strength, it is necessary to increase the use amount of cellulose as a main raw material. There is. On the other hand, when long fibers are used,
The reinforcing effect can be obtained with a relatively small amount, and the range of mechanical properties that can be adjusted is wide. Preferred fibers include paper pulp,
And filter paper powder. The average fiber length is preferably about 2.0 to 5.0 mm and the average width is about 20 to 50 μm. If the fiber length is short, a sufficient reinforcing effect cannot be obtained, and if the fiber length is too long, no further effect is obtained, and the uniform dispersibility and the handling property are reduced. Since the raw material fiber must have affinity for chitosan and fixability,
In some cases, it may be immersed in an acidic solution for a certain period of time or may be subjected to oxidation treatment or the like. This is because if the fixability with chitosan is weak, the strength tends to decrease.

Next, chitosan which can be used in the present invention is a deacetylated product of chitin, and can be used regardless of the production method. The degree of polymerization and the degree of deacetylation of chitosan affect the solubility, fixability, stability, etc. of chitosan.The lower the degree of polymerization, the better the solubility and fixability, but the strength of the structure increases. It tends to decrease, and the lower the degree of deacetylation, the lower the reactivity and the lower the solubility. In consideration of these properties, it is preferable that the degree of polymerization of chitosan is 100 or more and the degree of deacetylation is 60% or more.

If the fiber content is not high, the strength increases, but the structure tends to be weak and the elasticity tends to decrease,
On the other hand, if the amount is too small, it is difficult to obtain sufficient strength.
This is because the network of fibers is involved in the strength of the structure. This structure is significantly different from, for example, that a structure constructed using micronized cellulose is like a concrete matrix.

Next, a feature of the structure of the present invention is that it is porous in addition to the above-mentioned raw materials. Because it is a porous body, it is possible to obtain lightweight and sufficient strength,
Further, the range of imparting desired mechanical properties is widened. The bulk specific gravity of the porous material is usually about 0.01 to 0.1 g / cc, but may be appropriately set depending on the intended use of the structure. The hole diameter is not particularly limited, and may be designed in relation to the desired mechanical characteristics. Usually 1
It may be about 0 to 500 μm. If the bulk specific gravity is small and the pore size is large, the structure is rich in elasticity and the strength is reduced. On the other hand, if the bulk specific gravity is large and the pore size is small, the structure becomes hard and increases the strength.

By the way, since this structure contains chitosan, its mechanical properties are affected by water. No special treatment is required for a water-soluble structure, but in the case of a water-resistant structure, a chitosan insolubilization treatment is required. That is, when the obtained structure is immersed in water,
As the chitosan forming the structure dissolves in water,
The fibers of the porous body are loosened and dispersed in water. Therefore, it can be used as a water-soluble material, but is not used as a water-insoluble material. Then, the porous body can be insolubilized by acetylation with acetic anhydride or the like to partially chitinize the chitosan. Thus, a porous body insoluble in water can be obtained, and the solubility in water can be changed by adjusting the degree of acetylation. Usually, even when chitosan having a degree of deacetylation of 60% or more is used as a raw material, the degree of acetylation of the final product is about 40% to 50% due to the use of an acetic acid solution or the like. Since water resistance cannot be expected at this degree of acetylation, acetylation treatment is performed to reduce the acetylation degree to 60%.
Water resistance can be attained by setting it to 70% or more. Therefore, in the present invention, in order to obtain the desired mechanical properties of the structure and its water resistance, it can be appropriately adjusted according to the fiber length, the mixing ratio of chitosan / fiber, the bulk specific gravity, the pore size and the degree of acetylation. Can be prepared.

Next, a method for preparing the structure of the present invention will be described. First, a mixed solution composed of water, chitosan, fiber and acid is prepared. Since the acid concentration of the solution is about 0.5N and chitosan generally dissolves to 2% by weight, the concentration is appropriately adjusted. In addition, acetic acid, lactic acid, citric acid, hydrochloric acid and the like can be used as the acid.

After the solution is prepared, foaming is performed. As a method of foaming, a method of mixing a pyrolytic foaming agent such as sodium hydrogencarbonate or ammonium hydrogencarbonate or a reactive foaming agent such as baking powder to which an acidic agent is further added, or mechanically blowing air with a mixer or the like. A commonly used method such as a mixing method may be used.

Next, the acetylation can be carried out, for example, by immersing in a solution of an organic acid anhydride such as acetic anhydride or exposing the solution to a gaseous atmosphere. The higher the degree of acetylation, the lower the solubility and the higher the stability. Normally,
In gas, about 68% can be acetylated in one hour. It should be noted that, even if the processing is continued overnight, a horizontal buyout occurs at about 70%. Drying of the structure is usually 100 to 150 ° C., 3 to 12
It can be implemented in about an hour.

According to the present invention, the pore diameter of the porous body can be adjusted by changing the length of the plant fiber used and the concentration of chitosan. That is, when a fiber having a short fiber length is used and the concentration of chitosan is increased, the pore diameter becomes smaller. Conversely, when the fiber length is increased and the chitosan concentration is reduced, a product having a large pore size can be obtained. Further, the porosity of the porous body can be changed by adjusting the state of foaming by changing the concentration and components of the foaming agent. The mechanical properties such as the elastic modulus and the breaking strength change depending on the porosity and the pore size.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on embodiments.

Embodiment 1 FIG. Paper pulp (average fiber length 1mm, width 50μ) in 100cc water
m; 1 g of Toyo Roshi) and chitosan (degree of polymerization: about 200
0, degree of deacetylation 80), and 1 g of acetic acid was added with stirring. After sufficiently stirring until the chitosan and the pulp were completely dispersed, 5 g of ammonium bicarbonate was added thereto as a foaming agent, and the mixture was further stirred and dried at 150 ° C. for 3 hours using a hot air drier. During drying, the blowing agent decomposed and generated gas, forming a porous structure. The obtained pulp-chitosan complex was a porous water-soluble material having a degree of acetylation of 48%, a bulk density of about 0.01 g / cc, and an average pore diameter of 500 μm. When the mechanical properties of this product were examined, the tensile strength was 0.2 to 0.5 kgf / cm ² .

Embodiment 2 FIG. 1 g of the same paper pulp and 1 g of chitosan as in Example 1 were mixed with 100 cc of water, and 1 g of acetic acid was added with stirring. After sufficiently stirring until the chitosan and the pulp were completely dispersed, 5 g of baking powder was added thereto as a foaming agent, followed by drying at 120 ° C. for 3 hours with a hot air drier. The obtained pulp-chitosan complex was immersed in an acetic anhydride solution for 1 hour, and then neutralized by immersion in 1% sodium hydroxide.
This was sufficiently washed with water and dried naturally to form a porous body. The pulp-chitosan porous body thus produced has a degree of acetylation of 70% and a bulk density of 0.04 g / c.
c, having an average pore diameter of 100 μm, insoluble in water because chitosan is partially chitinized, and having a tensile strength about 2 to 5 times higher than before acetylation (1 to 3 kg)
f / cm ² ).

[0019]

The structure according to the present invention has the following features. (1) Mechanical properties such as elastic modulus and tensile strength can be controlled by changing the ratio of fiber to chitosan. (2) The porosity can be changed in a wide range by adjusting the state of foaming. (3) It is porous and has excellent water absorption. (4) The antibacterial properties of chitosan can be expected. (5) It can be used as a biodegradable material. Therefore, the structure according to the present invention can be applied in various fields,
For example, wound covering materials utilizing properties such as water absorption, biocompatibility, antibacterial properties, nursery beds for hydroponics utilizing water supply / drainage properties and antibacterial properties, cell immobilization carriers utilizing water supply / drainage properties and biocompatibility, porous Insulation material using the nature and natural material,
It can be applied to filters and the like utilizing porosity and adsorptivity.
As described above, according to the present invention, a composite porous body of fiber and chitosan can be prepared very easily, and its properties are used to produce biotechnology-related materials, pharmaceutical materials, agricultural materials, packaging materials, and the like. Is very useful for industry.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-2303 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08J 9/00-9/42 C08L 1 / 00-1/32 C08L 5/08

Claims (4)

(57) [Claims] [Claim 1] chitosan and issued to the plant fiber as the main raw material
A chitosan composite porous material having a bulk specific gravity of 0.01 to 0.1 g / cc. 2. Mixing water, chitosan, vegetable fiber and acid
Foamed and dried mixed solution consisting of chitosan and
And a plant fiber as a main raw material.
A chitosan composite porous material having a weight of 01 to 0.1 g / cc. 3. The plant fiber has an average fiber length of 2.0 to 5.0.
The chitosan composite porous body according to claim 1 or 2 , having an average width of 20 to 50 µm. 4. A structure containing chitosan and vegetable fiber as main raw materials.
A method for preparing a chitosan composite porous material having a bulk specific gravity of 0.01 to 0.1 g / cc, comprising a mixture of water, chitosan, plant fiber, and an acid. The above preparation method comprising the steps of foaming, drying and, if necessary, adjusting the degree of reacetylation to 40% or more.